Datasheet

108
7593L–AVR–09/12
AT90USB64/128
Figure 14-9. Timer/Counter timing diagram, with prescaler (f
clk_I/O
/8).
Figure 14-10 shows the setting of OCF0B in all modes and OCF0A in all modes except CTC
mode and PWM mode, where OCR0A is TOP.
Figure 14-10. Timer/Counter timing diagram, setting of OCF0x, with prescaler (f
clk_I/O
/8).
Figure 14-11 shows the setting of OCF0A and the clearing of TCNT0 in CTC mode and fast
PWM mode where OCR0A is TOP.
Figure 14-11. Timer/Counter timing diagram, clear timer on Compare Match mode, with pres-
caler (f
clk_I/O
/8)
14.8 8-bit Timer/Counter register description
14.8.1 TCCR0A – Timer/Counter Control Register A
TOVn
TCNTn
MAX - 1 MAX BOTTOM BOTTOM + 1
clk
I/O
clk
Tn
(clk
I/O
/8)
OCFnx
OCRnx
TCNTn
OCRnx Value
OCRnx - 1 OCRnx OCRnx + 1 OCRnx + 2
clk
I/O
clk
Tn
(clk
I/O
/8)
OCFnx
OCRnx
TCNTn
(CTC)
TOP
TOP - 1 TOP BOTTOM BOTTOM + 1
clk
I/O
clk
Tn
(clk
I/O
/8)
Bit 76543210
COM0A1 COM0A0 COM0B1 COM0B0 ––WGM01 WGM00 TCCR0A
Read/write R/W R/W R/W R/W R R R/W R/W
Initial value 0 0 0 0 0 0 0 0